Along with the recent advent of information technology (IT), IP telephone services have been provided on the basis of Voice over IP (VoIP) in addition to the conventional public telephone service (Plain Old Telephone System, POTS).
In such circumstances, by connecting a communication terminal as conventionally used such as an analog telephone terminal to a terminal connection device, i.e., a VoIP gateway through which a packet network (IP network) provided for IP telephone service is connected to a public switched telephone network (PSTN) for providing a plain old telephone system, this communication terminal is available for communication with another communication terminal through either or combination of the packet network and the public switched telephone network.
Also, since a packet network and a public switched telephone network are connected together through a gateway device which performs a predetermined signal conversion, the above communication terminal can communicate with other communication terminals which are connected only to the public switched telephone network.
However, there is a problem that the user of the above communication terminal must confirm whether or not the communication with the destination communication terminal is possible through the packet network and instruct the terminal connection device to use which of the packet network and the public switched telephone network for communication.
Then, taking into consideration the above circumstances, it is an object of the present invention to provide a terminal connection device, a connection control device and a multifunctional telephone terminal, with which it is determined which of the packet network and the public switched telephone network is used for communication on the basis of the destination telephone number, and if the packet network cannot be used the communication is performed through the public switched telephone network while the user is informed of the communication path used for communication with the destination communication terminal.